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Colloid and Polymer Science

, Volume 271, Issue 7, pp 680–687 | Cite as

Studies of the wetting kinetics of liquid drops on solid surfaces

  • A. Zosel
Original Contributions

Abstract

The viscosityηL and the surface tensionγL of the liquid as well as the equilibrium contact angleθe are essential parameters governing the wetting kinetics of liquids on solids. By means of a contact angle apparatus with video image digitization, the dynamic contact angle θ and the radiusr of the contact area of sessile drops on solid surfaces have simultaneously been determined in dependence on time after drop application between about 3·10−2 s and long times.

The measurements were performed with series of liquids: polydimethylsiloxanes with different molecular masses and solutions of polyisobutylene in decalin and polyacrylic acid in water, covering a wide range of concentrations. The liquids in each series have a constant surface tension, but viscosities ranging over about four orders of magnitude, allowing the influence ofηL andγL to be studied independently. Solids such as glass, polyethylene and polytetrafluoroethylene were chosen so that the cases of complete wetting (spreading) and partial wetting (θe) could be studied.

The curves of cosθ andr/R0 vs. time for the different liquids of a series can be superimposed to a master curve by plotting them againstγL·L·R0, whereR0 is the radius of the original drop. All these master curves coincide at small wetting times, with exception of the data for the polysiloxanes. That means that the early stage of the wetting process is determined only by the properties of the wetting liquid. The influence of the solid surface, characterized by the equilibrium contact angleθe becomes significant only at the end of the wetting process.

Key words

Surface tension viscosity dynamic contact angle sessile drop video image digitization 

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Copyright information

© Steinkopff Verlag 1993

Authors and Affiliations

  • A. Zosel
    • 1
  1. 1.Kunststofflaboratorium, Polymerphysik, FestkörperphysikBASF AGLudwigshafen am RheinGermany

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